Description

Hi all recently bought a new toy (see archive)

What I need to know is where does the outlet on the top of the blue valve need to go to.

Hope some one can help

cheers jon

That's your fuel pressure regulator. Just leave it open, it's just a breather for the diaphragm inside from memory. We use them all the time at work and they never get connected.

It connects to the inlet manifold so that a vacuum pulls the diaphragm.. Most don't connect it.

Dave B

Hmm that's a tricky one, if it's the FPR reference it would normally go to the manifold to maintain a constant pressure differential across the injectors. With no plenum that's obviously a bit tricky and I think a lot of bike negines use a sort of "mini plenum" that connects all 4 ports with very small diameter hoses to provide a constant load reference.

Could just leave it, it's less ideal for control but can be worked around with correct mapping.

thanks for the reply's. its a pain in the arse to start could this be affecting the starting???

How would I connect it to the inlet and does it just need to connect to one inlet tract or all four??

Cheers jon

How is it fueled? If it's injection (hence the throttle bodies, not carbs) then it will probably have been mapped with it like that so I wouldn't change it, as you'll affect the rest of the running and it should not change the starting. It's useful purely to get a more linear flowrate-to-dutycycle curve when tuning (meaning you can make more sensitive adjustments at idle,andaccount for boost if turbocharged) so there's no NEED to have it connected, it can just help if it's needed.

If you were to connect it you'd need to do some experimentation, which won't be easy or useful unless you really know what you're up to.

[Edited on 19/2/14 by coyoteboy]

It really needs connecting, you need to tap into all the TB's between the butterfly and head, there should be barbs then collect into a single pipe and plug into the FPR.

If the signal is very bouncy then add something like a small fuel filter to act as an air reservoir.

It will affect starting, not a huge change as it depends how much throttle you apply when starting, and it depends if you car is mapped having it connected. as the car starts it draws a vacuum on the pipe which lowers the fuel pressure so really affects throttle off idle and fuel on the overrun.

Regards Mark

I don't think it'll affect starting much at all, I've never seen <80% load during cranking with TBs on a few engines, so it won't be having much effect. I've mapped identical engines both with and without and not seen a noticeable difference other than in the values in the table (hence thinking it'll be fine unless he has a problem he wants to fix)

[Edited on 19/2/14 by coyoteboy]

depends if its been mapped or not,

it adds fuel pressure based on vac pressure

they can be mapped with fixed rate fuel pressure, 3 or 3.5 bar looking at the reg or if connected its a 1-1 rising rate reg so will see a max of not a clue at the moment

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Originally posted by mark chandler
It really needs connecting,

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thanks for the replys.

If it makes any difference the throttle bodies are jenvery and running omex management.

Also its on a base map according to the previous owner.

Ive never run a car with throttle bodies and management. Its just a real pain in the arse to start and was not sure if this could be the problem.

cheers jon

Base maps are, generally, designed for a bone-stock engine system with no account taken for mods, potential critical changes and finessing of starting/drivability. They're just there purely to get it moving so it can be taken to a proper rolling road.

Get the FPR hooked up properly and get it to a rolling road, I'm fairly sure you'll see a world of difference from a generic map!

Very few N/A cars have regulators that have the vacuum pipe fitted to the manifold especially on installs using individual throttle bodies. To get a meaningful vacuum with no spikes it would be necessary drill all the headers and link them together. After all that work and the necessary re-map there would be little (if any) improvement to the way the car runs.

Basically if the pipe is connected the fuel pressure varies with your throttle position. If its disconnected the fuel pressure remains constant at the pre set value (normally 3 bar).

Mapping with them connected is much more time consuming for no noticeable benefit. If the car is well mapped without them there is no need to fit them. Mine has run without them for over 9 years now with no issues. Some kits have clear instructions to leave the connection open to the atmosphere.

If it ain't broke don't fix it as they say. One less thing to go wrong.

And having the pipe disconnected will make no difference to your cold starting.

[Edited on 20/2/14 by Paul Turner]

[Edited on 20/2/14 by Paul Turner]

Never had the van pipe connected on the last 4 cars I've had with Tbs, including my current one.

dec666; if you fill in the location in your profile you may find there are people local to you

Thanks for all the reply's.

I am currently stripping the car down at the moment. and was just wanting to see if this was important. I shall leave it off for now until it goes to rolling road. but I will tap into the intake after I remove the engine just so the option is there when time comes to get it mapped.

Cheers all.

jon

quote:

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Basically if the pipe is connected the fuel pressure varies with your throttle position. If its disconnected the fuel pressure remains constant at the pre set value (normally 3 bar). Mapping with them connected is much more time consuming for no noticeable benefit

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quote:

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Originally posted by coyoteboy
You seem to be missing how they work.

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